The Karelian Isthmus (ru: Карельский перешеек) is the northwestern part of Leningrad Oblast. Much of it was part of Finland until the Second World War.
All passenger trains between Finland and Russia pass through the Karelian Isthmus and stop in Vyborg. Local trains (elektrishkas) from St. Petersburg serve the region, St. Petersburg itself being one of Russia's most important transit hubs.
It's likewise easy to get in by road; all buses and marshrutkas between St.Petersburg and southern Finland pass through the area and you're driving you will too.
There are three border crossings from Finland to the region:
See also: Boating on the Baltic Sea
In the summer there are cruises along the Saimaa Canal from Lappeenranta on the Finnish side to Vyborg. If you come and leave by boat and stay in Russia less than 72 hours you do so visa-free (check: you probably need to be part of a certified cruise). By own vessel you need visa and other documents.
Ladoga can be reached via the Russian waterways, from the Baltic Sea, the White Sea and the Black Sea.
The closest major airport is in St.Petersburg.
Primary administrative division